"The Invoice comprises the creation of an invoice that is sent from a seller to a buyer for payment for the goods or services detailed in the invoice supplied under conditions agreed between buyer and seller. An invoice may refer to goods, items or services related to one or more orders. An invoice may contain references to payment terms and transport information." (B4A)

"An invoice is a container data element that includes other data elements to convey a request for payment. The nature and number of the secondary data elements depends on the context in which it is being used" (B54)

2. An invoice contains a set of information, the minimum of which can be determined by adding together each parties legal, administrative, technical, geo-political and other requirements and finding a common superset. (B59)

3. An invoice payment request can be made in more than one single transaction (go away from document). (B5A)

4. The order in which an invoice is received within a specific transaction will vary greatly depending on the nature of that transaction. (B5B)

5. An invoice can be "implied" ( A quote with a prepayment demand serialized inline??) (B5C)

"what about the fact that an invoice resolves around payment for goods or services received. Then, taking that (and to Mike's and Duance's points), we have a transfer of resources (goods/services in exchange for payment). In the EAN.UCC drafts I've seen they have the notion of a commitment document (not a PO or a contract). Could this be related?" (B5E)

If an invoice is a response to an order, what if the order is not fulfilled? Is the invoice still appropriate? (B5O)

If the order calls for 100 items and only 50 are delivered, should the invoice be for 100 or 50? (B5P)

A claim may also be made for the failure to fulfill a commitment, for example a penalty for late delivery or late payment. Such penalties may be added to invoices. What is the ontological basis for such claims? (B5Q)